soc: mediatek: place Kconfig for all SoC drivers under menu

Add cleanup for placing all Kconfig for all MediaTek SoC drivers under
the independent menu as other SoCs vendor usually did. Since the menu
would be shown depending on "ARCH_MEDIATEK || COMPILE_TEST" selected and
MTK_PMIC_WRAP is still safe compiling with the case of "COMPILE_TEST"
only, the superfluous dependency for those items under the menu also is
also being removed for the sake of simplicity.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>